1. Technical Field
The present invention relates to an acceleration detector, and an acceleration detecting device and an electronic device with this acceleration detector.
2. Related Art
JP-A-1-302166 discloses a pendulum accelerometer (hereinafter referred to as acceleration detector) including a base, a pendulum rotation mass which is connected to the base via a hinge joint and can rotate about the hinge joint as a rotation axis, and a sensor unit which mediates the rotation mass to the base.
The acceleration detector is configured so that, as the rotation mass (hereinafter referred to as movable portion) rotates (hereinafter referred to as displacement) according to an acceleration applied, tensile stress or compressive stress is applied to the sensor unit (hereinafter referred to as acceleration detecting element) and thus causes change in resonance frequency of the acceleration detecting element, and the acceleration is detected based on the change.
In the acceleration detector, the displacement of the movable portion is regulated by a container (hereinafter referred to as package) housing the acceleration detector. That is, since the acceleration detector itself has no components for regulating the displacement of the movable portion, the movable portion and the acceleration detecting element are displaceable until these parts collide with an inner surface of the package.
Since the regulation of the displacement of the movable portion in the acceleration detector thus depends on the package as an external member, the space between the movable portion and the inner surface of the package may significantly differ from a preset value because of a number of dimensional tolerance factors related to the space between the movable portion (acceleration detecting element) and the inner surface of the package (for example, dimensional variation between respective components constituting the package, variation in fixing position of the acceleration detector to the package, and the like).
Therefore, in the acceleration detector, if the space between the movable portion and the inner surface of the package is larger than the preset value, the movable portion or the acceleration detecting element may collide hard with the inner surface of the package and may be damaged, depending on the magnitude of the acceleration applied.
Moreover, in the acceleration detector, if the space between the movable portion and the inner surface of the package is larger than the preset value, the movable portion or the acceleration detecting element may be damaged by displacement exceeding a limit of strength even though these parts do not collide with the inner surface of the package depending on the magnitude of the acceleration applied.
Meanwhile, in the acceleration detector, if the space between the movable portion and the inner surface of the package is smaller than the preset value, the displacement range of the movable portion is smaller than a preset range and therefore a preset acceleration detection range may not be covered.